Aqueous anionic functional silica slurry and amine carboxylic acid compositions for selective nitride removal in polishing and methods of using them

Abstract

The present invention provides aqueous chemical mechanical planarization polishing (CMP polishing) compositions comprising one or more dispersions of a plurality of elongated, bent or nodular anionic functional colloidal silica particles or their mixture with one or more dispersions of anionic functional spherical colloidal silica particles, one or more amine carboxylic acids having an isoelectric point (pI) below 5, preferably, an acidic amino acid or pyridine acid, and, preferably, one or more ethoxylated anionic surfactants having a C.sub.6 to C.sub.16 alkyl, aryl or alkylaryl hydrophobic group, wherein the compositions have a pH of from 3 to 5. The compositions enable good silicon nitride removal and selectivity of nitride to oxide removal in polishing.

Claims

1. An aqueous chemical mechanical planarization polishing composition comprising an abrasive of one or more dispersions of elongated, bent or nodular anionic functional colloidal silica particles or their mixture with one or more dispersions of anionic functional spherical colloidal silica particles, and one or more amine carboxylic acids chosen from glutamic acid, aspartic acid, nicotinic acid and picolinic acid having an isoelectric point (pI) from 2.0 to 4.0, wherein the compositions have a pH of from 3 to 5 and further wherein, the amount of the abrasive particles as solids, ranges from 0.01 to 30 wt. %, based on the total weight of the composition.

2. The aqueous chemical mechanical polishing composition as claimed in claim 1, wherein the total solids amount of the one or more amine carboxylic acids ranges from 0.005 to 5 wt. %, based on the total weight of the composition.

3. The aqueous chemical mechanical polishing composition as claimed in claim 2, wherein the total solids amount of the one or more amine carboxylic acids ranges from 0.01 to 1 wt. %, based on the total weight of the composition.

4. The aqueous chemical mechanical polishing composition as claimed in claim 1, further comprising one or more ethoxylated anionic surfactants having a C.sub.6 to C.sub.16 alkyl, aryl or alkylaryl hydrophobic group.

5. The aqueous chemical mechanical polishing composition as claimed in claim 4, wherein the ethoxylated anionic surfactant is chosen from ethoxylated sulfates, ethoxylated sulfonic acid, ethoxylated sulfonate salts, ethoxylated phosphates, ethoxylated phosphonates, or ethoxylated carboxylates.

6. The aqueous chemical mechanical polishing composition as claimed in claim 4, wherein the amount of the ethoxylated anionic surfactant ranges from 0.0001 to 1 wt. %, based on the total weight of the composition.

7. The aqueous chemical mechanical polishing composition as claimed in claim 1 having a pH of from 3.5 to 4.5.

Description

EXAMPLES

(1) The following examples illustrate the various features of the present invention.

(2) In the Examples that follow, unless otherwise indicated, conditions of temperature and pressure are ambient temperature and standard pressure.

(3) The following materials, including those listed in Table 1, below, were used in the Examples that follow:

(4) Surfactant A: Witcolate™ 1247H surfactant (Akzo Nobel, Arnhem, N L), a C.sub.6-C.sub.10 alcohol ethoxylated ammonium sulfate having 3 ethoxy groups, wherein C.sub.6 comprises 15-21% of the alkyl groups, C.sub.8 comprises 31-38.5% of the alkyl groups and C.sub.10 comprises 42-50% of the alkyl groups.

(5) TABLE-US-00001 TABLE 1 Elongated Silica and Other Abrasive Particles Concen- Aqueous Secondary tration.sup.2 Silica Particle size Raw (wt. % Slurry Source pH.sup.2 (DLS, nm) Materials solids) Slurry QUARTRON ™ ~5-7 30-40 TMOS 20 A  PL-1-D.sup.1 Slurry QUARTRON ™ ~5-7 60-80 TMOS 20 B  PL-3-D.sup.1 Slurry QUARTRON ™ ~5-7 60-80 TMOS 20 C* PL-3.sup.1 .sup.1Fuso Corp., Japan; .sup.2pH as delivered from source; *denotes comparative example.

(6) The various silica particles used in the Examples are listed in Table 1, above. Each of the silica Slurry A and Slurry B contained sulfonic acid functional groups. Comparative slurry, Slurry C does not contain the anionic functional groups of the present invention.

(7) The following abbreviations were used in the Examples that follow:

(8) POU: Point of use; RR: Removal rate.

(9) Isoelectric Points of Amine Carboxylic Acids: The isoelectric point or pI of an amine carboxylic acid is the pH at which the amine carboxylic acid does not migrate in an electric field or electrophoretic medium. For purposes of defining pI, pKas are assigned a numerical value from lowest pH to highest pH. Amine carboxylic acids having neutral side chains are characterized by two pKas: pKa1 for the carboxylic acid and pKa2 for the amine. The pI will be halfway between, or the average of, these two pKas, i.e. pI=½(pKa1+pKa2). At a pH below pKa1, the amine carboxylic acid will have an overall positive charge and at a pH above pKa2, the amine carboxylic acid will have an overall negative charge. For the simplest amine carboxylic acid, glycine, pKa1=2.34 and pKa2=9.6, pI=5.97. Acidic amine carboxylic acids have an acidic side chain. The pI will be at a lower pH because the acidic side chain introduces an extra negative charge. For example, for aspartic acid there are two acid pKas (pKa.sub.1 and pKa.sub.2) and one amine pKa, pKa.sub.3. The pI is halfway between these two acid pKa values, i.e. pI=½(pKa.sub.1+pKa.sub.2), so pI=2.77. Basic amine carboxylic acids have a pI at a higher pH because the basic side chain introduces an extra positive charge. For example, for histidine, pI is halfway between the two ammonia hydrogen pKa values, pI=½(pKa.sub.2+pKa.sub.3), so pI=7.59. The pI of many amine carboxylic acids is shown in Table 2, below.

(10) TABLE-US-00002 TABLE 2 Pkas And Isoelectric Points Of Amine carboxylic acids Amine carboxylic acid pKa1 pKa2 pKa3 pl Aspartic acid 1.88 3.65 9.6 2.77 Glutamic acid 2.19 4.25 9.67 3.22 nicotinic acid 2 4.85 3.425 picolinic acid 1.07 5.25 3.16 Cysteine 1.96 8.18 — 5.07 Asparagine 2.02 8.8 — 5.41 Phenylalanine 1.83 9.13 — 5.48 Threonine 2.09 9.1 — 5.6 Glutamine 2.17 9.13 — 5.65 Tyrosine 2.2 9.11 — 5.66 Serine 2.21 9.15 — 5.68 Methionine 2.28 9.21 — 5.74 Tryptophan 2.83 9.39 — 5.89 Valine 2.32 9.62 — 5.96 Glycine 2.34 9.6 — 5.97 Leucine 2.36 9.6 — 5.98 Alanine 2.34 9.69 — 6 Isoleucine 2.36 9.6 — 6.02 Proline 1.99 10.6 — 6.3 Histidine 1.82 6 9.17 7.59 Lysine 2.18 8.95 10.53 9.74 Arginine 2.17 9.04 12.48 10.76

(11) The following test methods were used in the Examples that follow:

(12) pH at POU: The pH at point of use (pH at POU) was that measured during removal rate testing after dilution of the indicated concentrate compositions with water to the indicated solids content.

Example 1

(13) Polishing and Removal Rate: Blanket wafer removal rate testing from polishing on each of tetraethoxy silane (TEOS), silicon nitride and amorphous silicon (aSi) substrates was performed using a Strasburgh 6EC 200 mm wafer polisher or “6EC RR” (Axus Technology Company, Chandler, Ariz.) at a downforce of 20.68 kpa (3 psi) and table and carrier revolution rates (rpm), respectively, of 93 and 87, and with an IC1000™ CMP polishing pad having a 1010 groove pattern (Dow, Midland, Mich.) and the indicated abrasive slurry, as shown in Table 3, below, at a given abrasive slurry flow rate 200 ml/min. A SEASOL™ AK45 AM02BSL8031C1 diamond pad conditioner disk (Kinik Company, Taiwan) was used to condition the polishing pad. The polishing pad was conditioned in situ during polishing using a down force of 3.17 kg (7.0 lbf) at 10 sweeps/min from 4.32 cm to 23.37 cm from the center of the polishing pad. The removal rates were determined by measuring the film thickness before and after polishing using a KLA-Tencor™ FX200 metrology tool (KLA Tencor, Milpitas, Calif.) using a 49 point spiral scan with a 3 mm edge exclusion. Removal Rate results and their ratios (selectively) are shown in Table 3, below.

(14) TABLE-US-00003 TABLE 3 Slurry Formulation Details, Removal Rates (RR) and Selectivities Zeta Solids Additive potential SiN RR TEOS RR, aSi RR SiN:TEOS SiN:aSi Ex. No. Slurry (wt. %) Additive (wt %) pH (mV) (Å/Min) (Å/Min) (Å/Min) RR ratio RR ratio  1* A 3 H.sub.3PO.sub.4 0.03 2.6 −38 722 23 99 31 7  2* A 3 H.sub.3PO.sub.4 0.06 2.3 −37 730 30 130 24 6 3 A 3 Nicotinic acid 0.05 4.0 −35 861 10 138 90 6 4 A 3 Nicotinic acid 0.1 3.6 −35 933 10 112 89 8 5 A 3 Nicotinic acid 0.2 3.5 −35 783 15 174 52 5 6 B 3 Nicotinic acid 0.05 3.8 −45 493 36 27 14 18 7 B 3 Nicotinic acid 0.1 3.7 −45 520 42 39 12 13 *Denotes Comparative Example.

(15) As shown in Table 3, above, the aqueous abrasive slurry compositions in Examples 3 to 5 provides having amine carboxylic acid with an isoelectric point of <5, all achieve a high nitride RR but a low oxide RR, thereby providing high nitride to oxide selectivity (˜100). Especially where the pH of the compositions lies at 4.0 or below. Such inventive examples provide good to excellent nitride to oxide polish selectivity. By comparison, the same compositions having phosphoric acid gave a lower nitride rate and a higher oxide removal rate. By comparison, the slurry B larger size abrasive particles provide lower nitride rate and higher oxide rate and, thus, lower nitride to oxide selectivity. Smaller size silica particles help increase nitride removal rate and lower oxide rate.

(16) The examples in Table 4 below, demonstrate that effect of anionic functional groups.

(17) TABLE-US-00004 TABLE 4 Slurry Formulation Details, Removal Rates (RR) and Selectivities Zeta Solids Additive potential SiN RR TEOS RR, aSi RR Ex. No. Slurry (wt. %) Additive (wt %) pH (mV) (Å/Min) (Å/Min) (Å/Min)  8* C 3 Picolinic acid 0.05 4.5 −8 663 54 12 10 B 3 Picolinic acid 0.05 4.2 −37 650 38 17 11 B 3 Picolinic acid 0.1 4.0 −35 771 38 20 *Denotes Comparative Example.

(18) As shown in In

(19) Table 3: Slurry Formulation Details4, above, the compositions of Example 10 and 11 exhibit higher SiN;Ox selectivity but same SiN RR compared to the composition of Comparative Example 8 in which silica is does not contain anionic functional groups. Higher zeta potential only favors low oxide rates but has no effect on SiN RRs.

(20) The Examples in Table 5, below, include surfactant A.

(21) TABLE-US-00005 TABLE 5 Slurry Formulation Details, Removal Rates (RR) and Selectivities Solids Nicotinic (wt. % acid Surfactant A SiN RR, TEOS RR, aSi RR, SIN:TEOS SIN:aSi RR Ex. No slurry A) (wt. %) (wt. %) pH Å/min Å/min Å/min RR ratio ratio 12 3 0.1 0.0 3.6 933 10 112 89 8 13 3 0.1 0.0125 3.55 851 9 10 94 83 14 3 0.1 0.025 3.53 831 10 8 87 99 * Denotes Comparative Example.

(22) As shown in Table 5, above, addition of Surfactant A C.sub.6-C.sub.10 alcohol ethoxylated sulfate) in the compositions of Examples 13-14 further improves SiN to aSi selectivity and is preferred over the compositions of Example 12.